Arrangement and method for increasing the measurement accuracy in the three-dimensional measurement of objects

Abstract

An arrangement for increasing measurement accuracy in three-dimensional measurement of objects, and a method for three-dimensional measurement of objects. The arrangement has a base for placing thereon an object to be measured, a device for emitting light beams toward the object, a device for detecting light beams reflected by the object and the substrate, and a device for determining 3D data based on travel time measurements and/or triangulation of the emitted light beams and reflected light beams, and for determining dimensions of the outer shell of the object. A measurement inaccuracy range affected by interferences and forming on the substrate is bridged and spaced from the actual measurement position by a transparent plate with a predetermined thickness arranged between the at least one object and the substrate, so that the determination of dimensions of the outer shell of the object is only partially possible and becomes more precise.

1 . An arrangement for three-dimensional measurement of objects comprising:
 a planar substrate for placing thereon at least one object to be measured;   an emitting device for emitting light beams in the direction of the at least one object;   a receiving device for detecting the light beams reflected from the at least one object and the substrate; and   a determining device for determining 3D data on the basis of time-of-flight measurements and/or triangulation of the emitted and reflected light beams and for determining the dimensions of the outer shell of the at least one object from the determined 3D data;   a transparent plate having a predetermined thickness for placement between the at least one object and the substrate, the thickness being higher than a measurement inaccuracy range forming on the substrate, the thickness being in a range between 1 and 50 millimeters   wherein the determining device corrects the determined 3D data or the determined dimensions of the outer shell of the at least one object by the thickness of the transparent plate ( 8 ), in that   the determining device first determines 3D data of the at least one object to be measured together with the transparent plate and the substrate, which serves as reference surface;   wherein   the determining device determines a virtual, planar separation plane running parallel to the reference surface and spaced apart from the latter by at least the thickness;   the determining device separates and eliminates the determined 3D data between the separation plane and the reference surface from the remaining determined 3D data; and   the determining device determines the dimensions of the outer shell of the at least one object on the basis of the remaining 3D data.   
     
     
         2 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the transparent plate is a plastic plate. 
     
     
         3 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the thickness of the transparent plate is in a range between 1 and 8 millimeters. 
     
     
         4 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the arrangement comprises at least one adjustable lifting column for spacing the transparent plate in height direction by a distance in a range of 0.1-20 millimeters from the substrate. 
     
     
         5 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the arrangement comprises an input device for manual or automated input of the thickness of the transparent plate and/or an input interface for receiving the distance between the transparent plate and the substrate measured by a measuring device. 
     
     
         6 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein:
 the emitting device, the receiving device and the determining device for the time-of-flight measurement of the emitted and reflected light beams are designed as a time-of-flight camera and/or as a LiDAR camera; or   the emitting device, the receiving device and the determining device for the triangulation of the emitted and reflected light beams are designed as a structured light camera and/or as a stereo camera.   
     
     
         7 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the substrate has an opaque surface and/or the transparent plate has, on the side facing the substrate, an opaque, light-reflecting, which reflects light falling through the transparent plate. 
     
     
         8 . The arrangement for three-dimensional measurement of objects according to  claim 7 , wherein the transparent plate has on the side facing the substrate a diffuse reflecting layer. 
     
     
         9 . The arrangement for three-dimensional measurement of objects according to  claim 8 , wherein the transparent plate has on the side facing the substrate a diffuse reflecting layer which is a plastic hard foam layer. 
     
     
         10 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the transparent plate has at least one layer of electrochromic glass. 
     
     
         11 . The arrangement for three-dimensional measurement of objects according to  claim 10 , wherein the at least one layer of electrochromic glass has an adjustable transmittance. 
     
     
         12 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the transparent plate has at least one replaceable transparent layer, as protective film, made of plastic, which protects the transparent plate from surface damage, like scratches, so that the optical properties of the transparent plate remain unchanged. 
     
     
         13 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the transparent plate has polarizing properties. 
     
     
         14 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the substrate is formed by a supporting surface of a balance. 
     
     
         15 . The arrangement for three-dimensional measurement of objects according to  claim 1 , wherein the transparent plate is designed as part of an electrically controlled display. 
     
     
         16 . The arrangement for three-dimensional measurement of objects according to  claim 15 , wherein the electrically controlled display is a LCD or OLED display. 
     
     
         17 . A method for three-dimensional measurement of objects, comprising the steps of:
 placing at least one object to be measured on a planar substrate;   emitting light beams in the direction of the at least one object and detecting the light beams reflected by the at least one object and the substrate;   determining 3D data based on time-of-flight measurements and/or triangulation of the emitted and reflected light beams; and   determining the dimensions of the outer shell of the at least one object from the determined 3D data,   arranging a transparent plate with a predetermined thickness between the at least one object and the substrate, the thickness being greater than a measurement inaccuracy range forming on the substrate, the thickness being in a range between 1 and 50 millimeters;   correcting the determined 3D data or the determined dimensions of the outer shell of the at least one object by the thickness of the transparent plate, determining 3D data of the at least one object to be measured together with the transparent plate and the substrate serving as reference surface;   determining a virtual, planar separation plane running parallel to the reference surface and spaced from it by the thickness;   separating and eliminating the determined 3D data between the separation plane and the reference surface from the remaining determined 3D data; and   determining the dimensions of the outer shell of the at least one object from the remaining 3D data.   
     
     
         18 . The method for three-dimensional measurement of objects according to  claim 17 , wherein the transparent has a thickness of between 1 and 8 millimeters.